I agree. They likely feel guilty for the way Brian turned out and believe any lame story he told them about Gabby.
He could have told them Gabby dumped him and flew to her parents house. Or he dropped her off at a friend’s house.
That would explain why he drove home alone.
So he had 10 days before Gabby’s parents called looking for her. The story he told his parents probably changed many times.
“So he had 10 days before Gabby’s parents called looking for her. “
The parents called many times starting much earlier. They even went to the police days before the official missing report date.